TiAl Turbomachine Blanks from Ingot Casting to Cut Porosity
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Solution Overview
Problem
The manufacturing of titanium-aluminum intermetallic alloy parts for turbomachine blades is hindered by difficulties in foundry and machining, including porosity issues, material loss, and the need for costly hot isostatic pressing, as well as challenges with lost-wax casting and centrifuged permanent mold methods, which result in suboptimal microstructure and mechanical properties.
Innovation Solution
A method involving plasma torch melting in a retractable mold to produce ingots, which are then cut into simpler shapes and machined to achieve the final complex shape, with heat treatment to promote duplex microstructure and minimize porosity and material loss, using PAM furnaces to control defects and achieve homogeneous, high-quality semi-finished products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lost-wax casting is used to obtain over-thickened raw material, then the raw material can be obtained, but material loss increases and rare materials like Yttrium are required for the mold shell
Solution Approach 1:
The invention changes the casting parameters by using a permanent mold with controlled cooling rates and temperature gradients, enabling direct casting of near-net-shape components without requiring over-thickened raw material. This eliminates the need for excessive material removal while avoiding the use of rare materials like Yttrium in mold shells.
Solution Approach 2:
The invention replaces the lost-wax mechanical process with a direct permanent mold casting system that uses controlled solidification and cooling mechanisms. This substitution eliminates the need for wax patterns, shell molding, and subsequent material removal, directly producing components with minimal material loss.
2Productivity
If centrifuged permanent mold casting is used to manufacture several turbomachine parts, then productivity increases, but the shell development becomes complex with compromise between resistance to centrifugation force and friability for demoulding
Solution Approach 1:
The invention extracts the complex shell development requirement by using a permanent mold system that eliminates the need for fragile shell structures. The permanent mold can directly withstand centrifugation forces without requiring compromise between strength and friability, as the mold is designed to be reused and does not need to be broken for demoulding.
Solution Approach 2:
The invention applies dynamic control during casting by adjusting centrifugation speed and molten metal flow rates to optimize solidification patterns. This dynamic control enables the production of multiple parts with consistent quality while simplifying the mold design, as the permanent mold structure remains fixed and does not require complex shell development.
3Reliability
If hot isostatic pressing is applied to close porosities, then porosity is reduced, but costs increase significantly and residual stresses are stored in the part
Solution Approach 1:
The invention performs preliminary action by optimizing the casting process itself to produce dense, low-porosity ingots through controlled solidification and feeding mechanisms. By preventing porosity formation during casting rather than attempting to close it afterward, the need for costly hot isostatic pressing is eliminated, and residual stresses are avoided.
Solution Approach 2:
The invention converts the potential harm of rapid solidification and porosity formation into a benefit by designing a casting system that uses controlled cooling rates and thermal gradients to promote dense solidification. The same rapid solidification that typically causes porosity is harnessed to create fine-grained structures with minimal defects, eliminating the need for additional porosity-closing treatments.
4Loss of substance
If near net shape casting is used to cast blank with almost final shape, then material loss decreases, but machining automation is compromised due to insufficient extra thickness
Solution Approach 1:
The invention applies local quality by providing different thickness characteristics in different regions of the cast blank. Critical areas have sufficient material thickness for automated machining, while non-critical areas maintain near-net-shape geometry. This regional differentiation enables both material efficiency and machining automation by allowing automated tools to operate in designated zones with appropriate material allowances.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces material loss, minimizes porosity and chemical segregation, and enhances mechanical and microstructural homogeneity, leading to efficient and cost-effective production of turbomachine parts with improved properties.
Implementation Method 1
maintain in fusion by plasma torch(es) and in a mold with a retractable bottom (or ring mold), an intermetallic alloy TiAl
Implementation Method 2
extract an ingot therefrom, as cast, in a cooled state melting
Implementation Method 3
heat treatment to promote duplex microstructure and minimize porosity and material loss
Data Source
AI summary
This involves manufacturing a metallic turbomachine component (19a,19b) comprising steps consisting in: a) using a plasma torch and a ring mould to melt a titanium-aluminium intermetallic compound, b) extracting an as-cast ingot therefrom, in a cooled casting state, c) cutting the ingot into at least one blank or rough form (21) of an exterior shape that is simpler than the complex shape of said component (19a,19b) that is to be manufactured, d) machining the blank (21) in order to obtain the component with said more complex exterior shape.